A while ago we had a lecture at the bee club on the use of Neam oil in
controlling varroa.  During the course of the talk the man said that some of
the most promising research seemed to lie in the area of medicating with
copper salts.  The report at
 www.beekeeping.com/articles/us/cupric_salts.pdf
seems to give good information.
Has anyone any experience or opinions on there use, or the reported
information?